Trans-Bronchial Needle Aspiration (TBNA) is a procedure utilizing a biopsy needle for obtaining tissue samples from the lung regions of a medical patient for purposes of examination and related procedures. During TBNA, the orientation of the insertion and the selection of a biopsy site for the needle are generally determined by a bronchoscopist, and typically, this is based on images obtained by computerized tomography (CT). As such, TBNA is a routinely used and relatively safe intervention for the diagnosis and staging of hilar lesions, these being lesions relating to lymph nodes of the lung. These are generally in the form of nodules. The specificity of the procedure is close to 100%, meaning that nearly all nodules identified as such by the procedure are in fact such nodules. See the paper by Win, T., et al. entitled “The role of transbronchial needle aspiration in the diagnosis of bronchogenic carcinoma,” Resp Care, June 2003; 48(6): 602-605.
The sensitivity of the procedure is variously reported to be between 47% and 73%, meaning the percentage of nodules found and identified as such by the procedure out of the set of actually existing nodules. See the publications by: Patelli, M., et al. entitled “Role of fiberoscopic transbronchial needle aspiration in the staging of N2 disease due to non-small cell lung cancer,” Ann Thoracic Surg, 2002; 73: 407-411; Xie, H. B. et al., entitled “Bronchoscopy Guided Transtracheal and Transbronchial Fine Needle Aspiration Biopsy: A 5-year institutional review of 111 cases,” Diagn. Cytopathol. 2002; 27(5): 276-281; and Harrow, E. M. et al., entitled “The utility of transbronchial needle aspiration in the staging of bronchogenic carcinoma,” Am J Respiratory Crit Care Med 2000; 161: 601-607.
The reasons for false negatives include insufficient tissue samples, non-relevant tissue samples, and biopsies made at wrong locations. Generally, the biopsy is carried out from within the airway wall in an outward direction and typically, the lymph nodes cannot be seen from inside the airway tube.
In a pilot study, McAdams et al. used virtual bronchoscopy to improve the orientation of TBNA by displaying the target volumes. The study was performed using single slice spiral CT. The patients underwent a CT thorax acquisition with 10 mm slice thickness. Additional 3-5 mm slices were obtained from patients with mediastinal or hilar lesions, which were then used for virtual bronchoscopy. The mediastinum is the space in the chest between the pleural sacs of the lungs that contains all the viscera of the chest except the lungs and pleurae.
Snapshots of relevant positions were taken and displayed together with the axial CT images during the bronchoscopy. The time required for calculating virtual endoscopy was 20-35 min, marking of the targets took 5 min and creating the film took another 30-60 min. The authors report a sensitivity of 88%, but did not compare the results to the traditional procedure. See the publication by McAdams, H. P. et al. entitled “Virtual bronchoscopy for directing transbronchial needle aspiration of hilar and mediastinal lymph nodes: a pilot study,” AJR 1998; 170: 1361-1364.
In another study, Hopper et al. create virtual endoscopy with marked target volumes from 3 mm CT images. TBNA was only executed virtually, based on axial CT only or virual bronchoscopy with overlayed target volumes. The authors describe a higher rate of success; however, the study is not based on clinical data. See the publication by Hopper, K. D. et al, entitled “Transbronchial biopsy with virtual CT bronchoscopy and nodal highlighting,” Radiology, 2001; 221: 531-536.
However, for conducting an investigation of an area of interest, typically the end portion of the endoscope needs to be bent through approximately a right angle so that the tip of the endoscope faces the area of interest, generally the lesion being examined. This is achieved by pushing in the endoscope so as to jam it against the side of the wall opposite the area of interest until the required orientation is achieved.
In a typical prior art procedure, the endoscope is pushed in, up to a reference point, such as down against the carina and the insertion reference depth of the actual endoscope is read off a scale on the endoscope. The endoscope is then withdrawn until the scale shows that the end of the endoscope should now be at the point where the lymph node is estimated to be, based on imaging. However, the actual withdrawal has to be somewhat less to make allowance for the length required for the right angle bend to enable the endoscope end to face the side wall. The endoscope is then pushed in so as to angle it against the wall and point it to where the lymph node is supposed to be. Some guesswork and estimation is required, particularly in view of the angle through which the end portion of the endoscope needs to be bent. Errors may occur in these estimations, causing the biopsy to miss the desired target.